1. Field of the Invention
The present invention relates to a sheet form epitaxial apparatus for forming an epitaxial layer on a surface of a substrate by supplying gas thereon.
This application claims priority from Japanese Patent Application No. 2005-375008, filed on Dec. 27, 2005, the content of which is incorporated herein by reference.
2. Background Art
There have been disclosed epitaxial apparatuses which form a silicon single crystal film (hereinafter referred to as “epitaxial film”) on a substrate by spraying gas on the substrate while heating by a heating device such as a heater (see, for example, Patent Document 1). In accordance with the aforementioned Patent Document 1, in order to spray the gas efficiently on the substrate supported by a susceptor (or a supporting member), the epitaxial apparatus includes an external wall surrounding the susceptor so as to prevent leakage of the gas sideways/laterally, an upper dome (or an upper lid member) mounted on the external wall on the surface side of the substrate so as to prevent leakage of the gas upward, and a susceptor ring (or an inner lid member) provided between the external wall and the susceptor so as to prevent leakage of the gas downward.
The upper dome is held between a clamp ring (or a holding member) and the external wall through an O ring or the like, and is held in a tight contact condition with both of the clamp ring and the external wall. The susceptor ring is provided in a removable manner on the external wall, for example, and is held in tight contact with the external wall when it is attached thereto. Moreover, in order to prevent the O ring from being distorted by the heat upon being heated, a circulation passage which enables a refrigerant such as water or the like to flow is formed inside the clamp ring; thereby cooling the portion held by the clamp ring and the external wall. Further, reaction products resulting from the generated gas upon being heated adhere to the upper dome and cause contamination of the upper dome. Therefore, the upper dome is formed so as to be cleaned by a chemical such as HCl gas or the like.
However, when the temperature of the clamp ring drops as it is cooled down, heat from other members which are in tight contact with the clamp ring moves to the clamp ring having a lower temperature; thereby generating a heat flow. Due to this heat flow, the heat from the upper dome tends to escape easily through the clamp ring to the open air, so that the temperature of the upper dome drops. As a result, the cleaning efficiency of the HCl gas deteriorates and the reaction products resulting from the generated gas upon being heated tend to remain on the upper dome.
Furthermore, being affected by the heat flow, heat from the susceptor ring moves from the external wall to the clamp ring, so that the heat tends to escape easily from the clamp ring into the open air. Thus, the temperature of the susceptor ring also drops. Once the temperature of the susceptor ring drops, the temperature of peripheral portion of the susceptor which is in close proximity to the susceptor ring drops. Consequently, temperature distribution appears in the substrate supported by the susceptor, and the difference in thermal stress causes slippage in the substrate.
In view of the above circumstances, the object of the present invention is to provide an epitaxial apparatus which can reduce an amount of residual products in the upper lid member, and can prevent slippage which occurs on the substrate, by suppressing the heat flow and the temperature drop in the upper lid member and in the inner lid member when heat is applied.
(Patent Document 1) Japanese Unexamined Patent Application, First Publication No. 2001-126995